Method and implant for stabilizing two bone portions separated by a cut or fracture

ABSTRACT

In a human or animal patient, two bone portions separated by a cut or fracture are stabilized in a desired position relative to each other by bringing the two bone portions into this desired position, by pulling them against each other, by providing an opening having a mouth on a bone surface and reaching across the cut or fracture and walls in both bone portions, by inserting an implant into the opening and anchoring the implant in the walls of the opening with the aid of a material having thermoplastic properties and energy transmitted into the implant for in situ liquefaction of at least part of the material having thermoplastic properties. One exemplary application of the stabilizing procedure concerns the two tibial bone portions separated by tibial plateau leveling osteotomy in a canine patient suffering from cranial cruciate ligament damage or rupture in a stifle joint.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention is in the field of medical technology and concerns amethod and an implant for stabilizing two bone portions separated by acut or fracture in a human or animal patient, in particular forstabilizing two bone portions being separated by osteotomy.

Description of Related Art

Osteotomy is a surgical procedure in which a bone is cut with the aim ofbeing shortened, lengthened or re-aligned. Osteotomy is performed onhuman and animal patients mainly for realigning the load bearingsurfaces in joints and for realigning bone portions in particular in thefacio-maxillar region but also for re-aligning bone portions healedtogether with an undesired alignment relative to each other after afracture. The bone portions separated by the osteotomy procedure mostlyneed to be re-aligned in a desired position relative to each other andto be stabilized in this position for being able to heal together again.According to the state of the art, osteotomy sites are usuallystabilized with the aid of plates (e.g. metal plates) which arepositioned on the bone surface across the osteotomy cut and are fastenedin this position with the aid of bone screws or nails. According to thestate of the art, simple bone fractures are stabilized in the samemanner.

The named stabilization of cut or fractured bones with the aid of platesand bone screws is well established but it is of an only limitedefficiency, mainly because the plates are preformed and therefore are tobe available in a large number of different types for a large number ofdifferent applications and different patients. Furthermore, metallicplates and screws need to be removed in most cases, which make furthersurgery necessary when the cut or fractured bone is healed.

Well known applications of osteotomy concern e.g. human hip or kneejoints and serve for re-aligning the articular surfaces of the joint inorder to correct dysplasias and deformities by improvement of thealignment and/or the interaction of the articulating bones, or forrelieving arthritic pain by re-aligning partly damaged articularsurfaces to shift the bearing of the load from damaged to still healthyregions of the articular surfaces. Further well known osteotomyapplications concern mandible or maxilla re-alignment e.g. forcorrecting discrepancies in tooth positions, or concern the chin bonefor correcting or improving a person's profile. In veterinary medicineosteotomy is used e.g. for treating canine stifle joints suffering fromcranial cruciate ligament rupture or damage, by tibial plateau levelingor tibial tuberosity advancement, both these treatments serving forreducing tibiofemoral shear forces during weight bearing which shearforces become large enough for damaging the joint, when the cranialcruciate ligament is damaged.

BRIEF SUMMARY OF THE INVENTION

It is the object of the invention to provide a further method and animplant for stabilizing, in a human or animal patient, two bone portionsseparated by a cut or fracture, in particular bones having beensubjected to osteotomy or a simple fracture, wherein method and implantaccording to the invention compared with the state of the art is toallow treatment of a larger number of types of bones, types of patients,and types of cuts and fractures with the same method and the sameimplant. In addition, the method and implant according to the inventionare to be capable of rendering an operation for removing the stabilizingimplant unnecessary and they are to be suitable not only for opensurgery but in particular for minimally invasive surgery. It is afurther object of the invention to create a tool set for carrying outthe method according to the invention.

The named objects are achieved by the method, the implant, and the toolset as defined in the independent claims.

The basic idea of the invention is to use instead of the known platebeing fixed to the bone surface and reaching across the cut or fracturefor stabilizing the two bone portions separated by the cut or fracture,an implant which is positioned in the cut or fracture, i.e. between thebone portions, and anchoring the implant in the bone tissue below thebone surface on both sides of the cut or fracture with the aid of amaterial having thermoplastic properties and energy (in particularvibrational energy) transmitted into the implant for in situliquefaction of the material having thermoplastic properties. Thereinthe material having thermoplastic properties is arranged on the implantsuch that on liquefaction it flows into the bone tissue on both sides ofthe cut or fracture where, on re-solidification, it forms a positive fitconnection between the implant and the bone tissue and therewith aconnection between the two bone portions. In most cases, this connectionrenders the bone portions stable enough such that additionalstabilization measures such as a plate arranged on the bone surfaceacross the cut or fracture and fixed with screws thereon are not needed.

The technique of anchoring an implant in hard tissue such as bone tissuewith the aid of a material having thermoplastic properties andvibrational energy transmitted into the implant for in situ liquefactionof the material having thermoplastic properties is disclosed e.g. in thepublications U.S. Pat. No. 7,335,205, U.S. Pat. No. 7,008,226, US2006/0105295, US-2008/109080, US 2009/131947, WO 2009/109057, and WO2009/132472. The disclosure of all the named publications andapplications is enclosed herein by reference. Therein the thermoplasticmaterial needs to have mechanical properties suitable for a mechanicallysatisfactory anchorage of the implant in the hard tissue, and, in itsliquefied state, a viscosity that enables it to penetrate into naturalor beforehand provided pores, cavities or other structures of the hardtissue. Furthermore, an only relatively small amount of the material isliquefied such that no unacceptable thermal load is put on the tissue.

Suitable liquefaction connected with an acceptable thermal loading ofthe tissue and giving suitable mechanical properties of the positive fitconnections is achievable by using materials with thermoplasticproperties having an initial modulus of elasticity of at least 0.5 GPaand a melting temperature of up to about 350° C. and by providing suchmaterial e.g. on an implant surface, which on implantation is pressedagainst the hard tissue, preferably by introducing the implant in a hardtissue opening which is slightly smaller than the implant or byexpanding the implant in a bone opening which originally is slightlylarger than the implant (expansion e.g. by mechanically compressing orbuckling the implant). During implantation, the implant is subjected tovibration of a frequency preferably in the range of between 2 and 200kHz (preferably ultrasonic vibration) by applying e.g. the sonotrode ofan ultrasonic device to the implant. Due to the relatively high modulusof elasticity, the thermoplastic material transmits the ultrasonicvibration with such little damping that inner liquefaction and thusdestabilization of the implant does not occur, i.e. liquefaction occursonly where the liquefiable material is in contact with the bone tissueand is therewith easily controllable and can be kept to a minimum.

Instead of providing the material having thermoplastic properties on thesurface of the implant (disclosed e.g. in U.S. Pat. No. 7,335,205 orU.S. Pat. No. 7,008,226), it is possible also to provide the materialhaving thermoplastic properties in a perforated sheath and to liquefy itwithin the sheath and press it through the sheath perforation to thesurface of the implant and into the pores or cavities of the hard tissue(disclosed e.g. in U.S. Pat. No. 7,335,205, U.S. Pat. No. 7,008,226, WO2009/109057, and WO 2009/132472) and/or it is possible to liquefy theliquefiable material between two implant parts of which one is vibratedand the other one serves as counter element, the interface between thetwo implant parts being positioned as near as possible to the bonetissue (as disclosed in US 2009/131947, WO 2009/109057 and WO2009/132472).

It is possible also to exploit energy types other than vibrationalenergy for creating the local thermal energy needed for the in situliquefaction of the material having thermoplastic properties. Such otherenergy types are in particular rotational energy turned into frictionheat in substantially the same manner as the vibrational energy, orelectromagnetic radiation (in particular laser light in the visible orinfrared frequency range), which radiation is preferably guided throughthe material with thermoplastic properties and locally absorbed by anabsorber being contained in the material having thermoplastic propertiesor being arranged adjacent to this material (as disclosed in thepublications US 2009/131947 and WO2009/109057).

Materials having thermoplastic properties suitable for the device andthe method according to the invention are thermoplastic polymers, e.g.:resorbable polymers such as polymers based on lactic and/or glycolicacid (PLA, PLLA, PGA, PLGA etc.) or polyhydroxy alkanoates (PHA),polycaprolactone (PCL), polysaccharides, polydioxanes (PD)polyanhydrides, polypeptides or corresponding copolymers or compositematerials containing the named polymers as a component; ornon-resorbable polymers such as polyolefines (e.g. polyethylene),polyacrylates, polymetacrylates, polycarbonates, polyamides, polyester,polyurethanes, polysulfones, polyarylketones, polyimides,polyphenylsulfides or liquid crystal polymers LCPs, polyacetales,halogenated polymers, in particular halogenated polyolefines,polyphenylensulfides, polysulfones, polyethers or equivalent copolymersor composite materials containing the named polymers as a component.

Specific embodiments of degradable materials are Polylactides like LR706PLDLLA 70/30, R208 PLDLA 50/50, L210S, and PLLA 100% L, all ofBöhringer. A list of suitable degradable polymer materials can also befound in: Erich Wintermantel und Suk-Woo Haa, “Medizinaltechnik mitbiokompatiblen Materialien und Verfahren”, 3. Auflage, Springer, Berlin2002 (in the following referred to as “Wintermantel”), page 200; forinformation on PGA and PLA see pages 202 ff., on PCL see page 207, onPHB/PHV copolymers page 206; on polydioxanone PDS page 209. Discussionof a further bioresorbable material can for example be found in CABailey et al., J Hand Surg [Br] 2006 April; 31(2):208-12.

Specific embodiments of non-degradable materials are: Polyetherketone(PEEK Optima, Grades 450 and 150, Invibio Ltd), Polyetherimide,Polyamide 12, Polyamide 11, Polyamide 6, Polyamide 66, Polycarbonate,Polymethylmethacrylate, Polyoxymethylene, or polycarbonateurethane (inparticular Bionate by DSM, in particular type 65D and 75D). An overviewtable of polymers and applications is listed in Wintermantel, page 150;specific examples can be found in Wintermantel page 161 ff. (PE,Hostalen Gur 812, Höchst AG), pages 164 ff. (PET) 169ff. (PA, namely PA6 and PA 66), 171 ff. (PTFE), 173 ff. (PMMA), 180 (PUR, see table), 186ff. (PEEK), 189 ff. (PSU), 191 ff (POM—Polyacetal, tradenames Delrin,Tenac, has also been used in endoprostheses by Protec).

The material having thermoplastic properties may further contain foreignphases or compounds serving further functions. In particular, thethermoplastic material may be strengthened by admixed fibers or whiskers(e.g. of calcium phosphate ceramics or glasses) and such represent acomposite material. The material having thermoplastic properties mayfurther contain components which expand or dissolve (create pores) insitu (e.g. polyesters, polysaccharides, hydrogels, sodium phosphates),compounds which render the implant opaque and therewith visible forX-ray, or compounds to be released in situ and having a therapeuticeffect, e.g. promotion of healing and regeneration (e.g. growth factors,antibiotics, inflammation inhibitors or buffers such as sodium phosphateor calcium carbonate against adverse effects of acidic decomposition).If the thermoplastic material is resorbable, release of such compoundsis delayed.

Fillers used may include degradable, osseostimulative fillers to be usedin degradable polymers, including: β-Tricalciumphosphate (TCP),Hydroxyapatite (HA, <90% crystallinity); or mixtures of TCP, HA, DHCP,Bioglasses (see Wintermantel). Preferred composite materials containingsuch fillers are: PLDLA (Böhringer: LR706) filled with dibasiccalciumphosphate (weight ratio 70:30) and PLLA (Böhringer: L210S) filledwith TCP (weight ratio: 40:60).

Osseo-integration stimulating fillers that are only partially or hardlydegradable, for non degradable polymers include: Bioglasses,Hydroxyapatite (>90% cristallinity), HAPEX®, see S M Rea et al., J MaterSci Mater Med. 2004 September; 15(9):997-1005; for hydroxyapatite seealso L. Fang et al., Biomaterials 2006 July; 27(20):3701-7, M. Huang etal., J Mater Sci Mater Med 2003 July; 14(7):655-60, and W. Bonfield andE. Tanner, Materials World 1997 January; 5 no. 1:18-20. Embodiments ofbioactive fillers and their discussion can for example be found in X.Huang and X. Miao, J Biomater App. 2007 April; 21(4):351-74), J A Juhaszet al. Biomaterials, 2004 March; 25(6):949-55. Particulate filler typesinclude: coarse type: 5-20 μm (contents, preferentially 10-25% byvolume), sub-micron (nanofillers as from precipitation, preferentiallyplate like aspect ratio>10, 10-50 nm, contents 0.5 to 5% by volume).

Preferred embodiments of the implant according to the invention comprisea plurality of anchoring pins (preferably two), whose proximal ends areconnected with each other by at least one bridge portion (preferablyone). Such an implant e.g. comprises two anchoring pins equipped foranchorage in the bone tissue using one of the above shortly describedanchoring methods, the anchoring pins being connected by a bridgeportion, which may be equipped for osseointegration or, the same as theanchoring pins, for anchorage in the bone tissue. Between the distalends of the anchoring pins, the implant delimits an osteoconductionregion, in which the bone tissue of the two bone portions to bestabilized is kept in intimate contact with each other. A proximalimplant face is equipped for arranging the implant on a distal end of animplantation tool and for transmitting the energy necessary for the insitu liquefaction into the implant.

For positioning the implant between the two bone portions, these arebrought into the desired position relative to each other and in thisposition are pulled against each other in order to get into intimatecontact with each other. Then an opening is made in the bone tissue, theopening reaching across the cut or fracture separating the two boneportions to be stabilized, i.e. a mouth of the opening in the bonesurface reaches across the cut or fracture and a depth of the openingextends into the bone tissue substantially along the depth of the cut orfracture. The opening preferably comprises bores for accommodation ofthe anchoring pins, having a corresponding cross section, and mayfurther comprise a groove for the bridge portion or bridge portions. Theimplant is then positioned and anchored in the opening. The fixation ofthe bone portions is released only when the liquefied material hasre-solidified in the bone tissue on both sides of the cut or fractureand is therewith able to maintain the bone portions in the desiredposition and intimate contact with each other.

The groove provided for the bridge portion of the implant may have adepth corresponding to the depth of the bridge portion or, in particularfor a bridge portion tapering in a distal direction it may be sufficientto provide a groove which only concerns the cortical layer of the boneportions and to press the bridge portion into the underlying cancellousbone without previous removal of such cancellous bone.

As it is easily possible to make the whole implant from a bio-resorbableor bio-degradable material, the implant may be gradually replaced by newbone tissue bridging the cut or fracture at the place of the implant andtherefore the implant does not need to be removed in a second surgicaloperation. Alternatively the implant may at least partly be made of anon-resorbable or non-degradable material and remain in the bone forpermanently fixating the bone portions. This may be particularlyadvantageous in case of a bone whose healing capacity is impaired bydisease (e.g. osteoporosis) or old age.

There is no necessity for the implant according to the invention tocomprise any bone or bone replacement material; however, it may ofcourse do so. Bone growth enhancing material such as e.g. allograft orautograft bone material, bone replacement material, sponges, BMPcarriers, if used, are preferably arranged in the above namedosteoconduction region of the implant, i.e. between the distal ends ofthe anchoring pins, wherein the named materials may be positionedbetween the bone tissue of the two bone portions to be stabilized beforepositioning and anchoring the implant or wherein the named materials maybe preassembled with the implant. For such preassembly, implant surfacesaround the osteoconduction region may carry retention means such as e.g.grooves or dents for retaining the named material. For accommodation ofsuch materials, it will be advantageous to make room for them betweenthe two bone portions, i.e. to e.g. provide a groove between the boresof the opening in which the implant is to be anchored, the groove havinga larger depth than the bridge portion. The bridge portion will serve insuch a case for not only stabilizing the anchoring pins relative to eachother but also as means for preventing the above named materials fromexiting from between the bone portions.

Further embodiments of the implant and the method according to theinvention may vary from the above shortly described preferredembodiments as described hereinafter.

The anchoring pins and the bridge portion of the implant constituteseparate implant parts (multi-part or preferably three-part implantopposed to the above described one-part implant), wherein the anchoringpins are positioned and anchored in the opening first, and the bridgeportion is then mounted on the proximal ends of the anchoring pins, orwherein the bridge portion is positioned in the opening first and theanchoring pins are then pushed through or past the bridge portion andanchored in the bone tissue beside and/or beyond the bridge portion (seeFIGS. 13 and 14).

The implant does not comprise a bridge portion, i.e. it comprises only aplurality of anchoring pins (or even only one anchoring pin), wherein aplurality of anchoring pins is preferably implanted simultaneously.

The anchoring pins have any suitable cross sections and the openingparts for accommodating the anchoring pins are not bores but e.g.punched openings.

The bridge portion is plastically or resiliently bendable and theimplant is adapted by the surgeon to the form of the cut or fracture bybending the bridge portion.

For stabilizing two bone portions being separated by a cut or fracture,not only one but a plurality of implants is used depending on theapplication, on the size of the cut or fracture, and on the size of theimplant.

The implant does not comprise distinguishable anchoring pins and bridgeportions but has the form of a parallelepiped or wedge, a shortestextension extending across the cut or fracture, a longest extensionextending along the cut or fracture and a middle extension or taperingextension extending into the cut or fracture, wherein the openingprovided for the implant is a corresponding groove.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in further detail in connection with theappended Figs., wherein:

FIG. 1 is a perspective view of a preferred embodiment of the implantaccording to the invention;

FIG. 2 is an elevation view that shows the method and implant accordingto the invention used for stabilizing two tibial portions of a caninestifle joint after tibia plateau leveling osteotomy;

FIG. 3A is a plan view illustrating a first phase of an exemplaryembodiment of the method according to the invention;

FIG. 3B is a plan view illustrating a second phase of an exemplaryembodiment of the method according to the invention;

FIG. 3C is a plan view illustrating a third phase of an exemplaryembodiment of the method according to the invention;

FIG. 3D is a plan view illustrating a fourth phase of an exemplaryembodiment of the method according to the invention;

FIG. 3E is a plan view illustrating a fifth phase of an exemplaryembodiment of the method according to the invention;

FIG. 4 is a flow chart for the method as illustrated in FIGS. 3A-3E;

FIG. 5A is an elevation view of a cut finder;

FIG. 5B is an elevation view of a fixation/guide tool;

FIG. 5C is an elevation view of a drill guide;

FIG. 5D is an elevation view of a drill;

FIG. 5E is an elevation view of a cutter guide;

FIG. 5F is an elevation view of a cutter;

FIG. 5G is an elevation view of a control tool;

FIG. 5H is an elevation view of an implantation tool;

FIG. 6 is a flow chart of a method in which the whole tool set accordingto FIGS. 5A to 5H is used;

FIG. 7 is a sectional elevation view that shows an exemplary embodimentof the fixation/guide tool as used in the method according to theinvention for fixating the bone portions separated by the cut orfracture and for pulling the bone portions against each other;

FIG. 8A is a sectional elevation view of the implant;

FIG. 8B is a sectional plan view of the implant;

FIG. 8C is a partial sectional elevation view of the implant;

FIG. 9 is a sectional elevation view through a further one-part implantsimilar to the implants according to FIGS. 1 and 8A to 8C, the implantbeing mounted on the distal end of an implantation tool;

FIG. 10 is a sectional elevation view of a further exemplary embodimentof a one-part implant similar to the implants of FIGS. 1 and 8A to 8C;

FIG. 11 is a sectional elevation view of a further exemplary embodimentof a one-part implant similar to the implants of FIGS. 1 and 8A to 8C;

FIG. 12 is a sectional elevation view of a further exemplary embodimentof a one-part implant similar to the implants of FIGS. 1 and 8A to 8C;

FIG. 13 is a perspective view and a sectional elevation view that show afurther exemplary embodiment of the implant according to the invention,the implant comprising three separate parts to be introduced in thejoint in succession and to be assembled within the joint (three-part ormulti-part implant);

FIG. 14 is a plan view that illustrates an exemplary application of theimplant according to FIG. 13;

FIG. 15A is a plan view that shows a further embodiment of the implantaccording to the invention, which is based on the same principle as theimplant according to FIG. 13;

FIG. 15B is a sectional elevation view that shows a further embodimentof the implant according to the invention, which is based on the sameprinciple as the implant according to FIG. 13;

FIG. 16 is an elevation view of an anchoring pin and bridge portions;

FIG. 17 is an elevation view of anchoring pins and bridge portions;

FIG. 18 is an elevation view of anchoring pins and bridge portions; and

FIG. 19 is an elevation view of anchoring pins and a bridge portion.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a three-dimensional illustration of a preferred embodiment ofthe implant according to the invention. The implant comprises twoanchoring pins 1 and a bridge portion 2, arranged between the proximalends of the anchoring pins 1. The whole implant is preferably made of aresorbable thermoplastic polymer (e.g. of polylactide, preferably LR706by Böhringer). The anchoring pins 1 are slightly tapering and comprise apointed distal end, the surface of the slightly tapering region beingequipped with energy directors e.g. in the form of short axial ridgesarranged in a plurality of adjacent rings, wherein the ridges of onering are staggered in relation to the ridges of the adjoining ring orrings. Similar arrangements of energy directors are described in thepublication US 2008/0109007 the disclosure of which is enclosed hereinby reference.

The opening provided for implantation of the implant according to FIG.1, which opening reaches across the cut or fracture separating the twobone portions, preferably comprises two bores (possibly stepped) and agroove therebetween (see FIGS. 3A-3E) and is preferably dimensioned suchthat liquefaction and anchorage between device and bone tissue occursnot only on the surface of the anchoring pins 1 but also on the surfaceof the bridge portion 2. This means that the implant is slightlyoversized in comparison with the opening.

A proximal face 3 of the implant is preferably equipped, e.g. withaxially extending bores 4, for holding the implant on the distal end ofan implantation tool, as further discussed in connection with followingfigures. In the case of a fully thermoplastic and therewith x-raytransparent implant it is advantageous to design these openings deeperand to position marker elements therein. These marker elements comprisea material which is visible e.g. for an x-ray control of the implantposition after implantation. They consist e.g. of titanium, tantalum oranother suitable metal or they comprise a bioresorbable material, suchas e.g. a composite material of barium sulfate in PLA, which iseventually resorbed together with the rest of the implant.

If the implant according to FIG. 1 is fully made of a suitablethermoplastic material, in particular of such a material having arelatively low glass transition temperature, it is possible to transmitenough energy into the implant for bringing portions of the materialabove the glass transition temperature (in addition to liquefyingsurface material) such that they are capable of being slightly deformedand therefore better adapted to the form of the opening provided for theimplantation. Such deformation may e.g. concern the anchoring pins or itmay concern the bridge portion.

FIG. 2 illustrates the application of the method and the deviceaccording to the invention for stabilizing two tibial portions of acanine stifle joint after tibia plateau leveling osteotomy. FIG. 2 showsin a very schematic manner, the stifle joint before and after theosteotomy. Visible are the proximal end of the tibia 5 and the distalend of the femur 6, the tibial bone being cut into a distal portion 5.1and a proximal portion 5.2 by a half circular cut 5.3. The two boneportions 5.1 and 5.2 are re-aligned by rotating the portion 5.2 relativeto the portion 5.1 such that the tibia plateau is moved from a backwardssloping position into a substantially horizontal position as indicatedwith the dashed line denominated with TPO for tibia plateau orientation.

The two bone portions 5.1 and 5.2 are stabilized in the rotated positionby implanting an implant into the cut 5.3, the right hand part of FIG. 1showing the proximal face 3 of an implant according to FIG. 1.Advantageously the implant is implanted in the opening provided for theimplantation to a depth such that the proximal implant face 3 is aboutflush with the bone surface.

FIGS. 3A, 3B, 3C, 3D and 3E illustrate an exemplary embodiment of themethod according to the invention in five successive phases, wherein thebone portions 11 and 12 being separated by the cut or fracture 13 areviewed from the bone surface and wherein a distal face of afixation/guide tool being positioned on the bone surface for theimplantation of the implant 15 is illustrated in dash-dotted lines 15 onthis bone surface. The implant is similar to the one illustrated in FIG.1, an exemplary embodiment of the fixation/guide tool is shown in moredetail in FIG. 7.

In a first phase shown in FIG. 3A, the bone portions being separated bythe cut or fracture 13 have been brought into the desired positionrelative to each other and the distal face of the fixation/guide tool(lines 14) is fixated on the bone surface, e.g. with the aid of pricks(lines 14′) being punched into the bone surface, wherein at least thedistal end of the fixation/guide tool comprises two half portions, eachone being fixated on one of the bone portions 11 and 12 such that thedivision between the tool half portions is positioned along the cut orfracture 13.

In a second phase shown in FIG. 3B, the bone portions 11 and 12 arepulled against each other by forcing the two tool half portions towardseach other for closing the cut or fracture 13 completely and forbringing the two bone portions into intimate contact with each otherwhich is advantageous for good and fast healing.

In a third phase shown in FIG. 3C, an opening 15 adapted to the implant16 (phase d) to be implanted between the bone portions 11 and 12 isprovided. In the preferred embodiment of the method the openingcomprises two bores for accommodating the anchoring pins of the implantand possibly a groove for accommodating the bridge portion of theimplant, wherein the groove extends between the two bores, wherein thegroove has a lesser depth than the bores, and wherein the bores as wellas the groove involve both sides of the cut or fracture, i.e. the cut orfracture 13 between the two bone portions runs approximatelydiametrically through the bores and approximately midway through thegroove.

In a fourth phase shown in FIG. 3D, the implant 16 being adapted to theopening 15 is implanted and anchored in the opening 15, i.e. in bonetissue of both bone portions 11 and 12, such fixating the two boneportions in the desired relative position and in intimate contact witheach other.

In a fifth phase shown in FIG. 3E, the fixation/guide tool is removed,and therewith the stabilization procedure according to the invention iscompleted.

The features of the above described preferred embodiment of the methodaccording to the invention for stabilizing two bone portions beingseparated by a cut or fracture may be varied e.g. in the followingmanner without departing from the basic idea of the invention. The boneportions 11 and 12 can be held in intimate contact with each other notby distal half portions of a fixation/guide tool but by per se knownmeans such as e.g. a jig which is installed already for the osteotomy.The implant and the opening may have different forms as discussedalready further above.

FIG. 4 is a flow chart illustrating the main steps of the method asillustrated in FIGS. 3A-3E. These main steps are described hereinbelow.

The fixation step includes arranging the two bone portions in a desiredposition relative to each other, pulling them against each other, suchthat they are in intimate contact with each other along the cut orfracture, and fixating them in this position.

The preparation step includes providing an opening reaching across thecut or fracture, the form of the opening being adapted to the implant tobe used.

The implantation step includes introducing the implant into the openingand applying energy, preferably mechanical vibration, to the implanteither during introduction (if the liquefiable material is to beliquefied while being pressed against the bone tissue) or afterintroduction (if the liquefiable material is to be liquefied inside aperforated sheath and pressed through the sheath perforation and/or ifthe liquefiable material is liquefied between two device parts).

The finishing step includes releasing the fixation of the two boneportions established in the fixation step.

FIGS. 5A to 5G show the tools of an exemplary embodiment of the tool setaccording to the invention, the tool set serving for carrying out themethod. The tool set is e.g. suitable for implanting an implant asillustrated in FIG. 1 in a method as illustrated in FIGS. 3 and 4. Eachtool of the tool set is shown viewed from the side and against thedistal tool end. The tools, which are shown in the sequence of their usein the implantation method are the following: a cut finder 20 (FIG. 5A),a fixation/guide tool 21 (FIG. 5B), a drill guide 22 (FIG. 5C), a drill23 (FIG. 5D), a cutter guide 24 (FIG. 5E), a cutter 25 (FIG. 5F), acontrol tool 26 (FIG. 5G), and an implantation (preferably vibration)tool 27 (FIG. 5H). Tools 20 and 21 are applicable in the fixation step,tools 21 to 26 in the preparation step, and tools 21 and 27 in theimplantation step. The overall axial lengths of the tools is preferablyadapted to the application in which they are used. This means that thetools are relatively short when e.g. used on a canine stifle joint, butare longer when used e.g. on a human hip bone.

The cut finder 20 is equipped for finding the cut or fraction betweenthe bone portions and for marking the orientation of this cut orfracture on the bone surface. For this purpose it carries on its distalend at least one flat and preferably blunt protrusion (e.g. twoprotrusions 30) which is suitable for being pushed into the cut orfracture. The cut finder 20 may further comprise an axial bore 31 foraccommodating a K-wire (not shown) being used for locating the cut orfracture to start with, and for guiding the cut finder 20 towards thecut or fracture, wherein the cut finder 20 is pushed along the wire. Thecut finder 20 has a cross section with one distinguished larger diameterin the direction of the cut being located with the aid of the distalprotrusions or the direction defined by the protrusions respectively(the cross section is e.g. oblong as illustrated or oval but notcircular nor square), this cross section being adapted to the implant aswell as to inner or outer cross sections of the further tools of thetool set in a way to be elaborated further down.

The fixation/guide tool 21 comprises an axial tunnel 32 for guiding thefixation/guide tool 21 along the cut finder 20, i.e. the tunnel has across section which corresponds to the cross section of the cut finder20. As already discussed in connection with FIGS. 3A-3E, thefixation/guide tool 21 comprises at its distal end two tool halfportions 21.1 and 21.2 the section line between the two half portionsextending along the distinguished cross section diameter, a distal faceof each half portion being equipped with a plurality of short and sharpspikes 33 or blades suitable for fixing the fixation/guide tool to thebone surface on either side of the cut or fracture. As discussed infurther detail in connection with FIG. 7, the two distal half portions21.1 and 21.2 of the fixation/guide tool 21 are designed to resilientlyflare outwards, such that in a non-stressed configuration there is a gapbetween the distal faces of the two half portions. In the fixation step,the spikes are forced into the bone surface e.g. by applying a punch 34to the proximal tool end. Then the two half portions are forced againsteach other for pulling the bone portions fixed thereon against eachother (see FIG. 7) and the half portions are locked in the forcedposition for keeping the bone portions in intimate contact with eachother.

The drill guide 22 comprises two axial bores 35 adapted in diameter anddistance from each other to the diameter and the position of theanchoring pins of the implant. The outer cross section of the drillguide 22 is adapted to the cross section of the axial tunnel 32 of thefixation/guide tool 21 such that guidance of the drill guide 22 in thisaxial tunnel positions the two axial bores on the distinguished diameterand therewith over the cut or fracture. The drill guide 22 furthercomprises a stop shoulder 36, e.g. at its proximal end or inside theaxial bores.

The drill 23 being equipped for drilling bone tissue has a diameterbeing adapted to the diameter of the axial bores 35 of the drill guide22 and an axial length from a distal end to a depth stop, e.g. a regionof increasing diameter 37, which axial length is greater than the axiallength of the drill guide from a distal end to the stop shoulder 36 byabout the depth to which the anchoring pins of the implant are to beintroduced in the bores made with the drill.

The cutter guide 24 has substantially the same outer cross section asthe drill guide 22 and comprises an axial tunnel 38 which has an oblongcross section extending along the distinguished diameter and beingadapted to the proximal face of the bridge portion of the implant. Thecutter guide 24 further comprises a stop shoulder 39, e.g. on itsproximal end as illustrated, or inside the axial tunnel 38.

The cutter 25 is preferably a rotating tool equipped for removing bonetissue from between the two bores produced with the aid of the drillguide 22 and the drill 23. The cutter 25 is e.g. a drill having a crosssection adapted to the smaller extension of the cross section of tunnel38 and preferably being mounted to a rotational drive such that it canbe laterally displaced or pivoted relative to a housing of the drive inthe plane of the longer extension of the cross section of tunnel 38 in avery limited manner. The cutter may also be designed as acorrespondingly shaped punching tool being e.g. driven by ultrasonicvibration. Such punching tools are disclosed in the publication US2008/269649, the disclosure of which is enclosed herein by reference.The cutter 25 further comprises a depth stop 40 cooperating with thestop shoulder 39 of the cutter guide 24. The axial length of the cutter25 from its distal end to the depth stop 40 is larger than the axiallength of the cutter guide 24 from its distal end to the stop shoulder39 by the depth to which the tissue between the two bores is to beremoved, preferably at least by the depth of the bridge portion of theimplant.

The control tool 26 has a distal end similar to the implantation tool 27carrying the implant (see below) but slightly undersized and, adjoiningthis distal end, it has a cross section which is the same as the outercross section of drill guide and cutter guide. The control tool 26advantageously carries depth marks (not shown) where it protrudes fromthe fixation/guide tool 21, the marks indicating depths to which thedistal end of the control tool is introduced in the opening producedwith the drill 23 and the cutter 25.

The implantation tool 27 is e.g. a sonotrode which is equipped for beingcoupled to a vibration drive, e.g. of an ultrasonic device. The distalend of the implantation tool 27 is equipped for holding the implant 16and for transmitting energy (e.g. vibration) to the implant. For thelatter function, it is preferable for the distal face of theimplantation tool 27 to be adapted exactly to the proximal face of theimplant 16. In an area between the distal end and the proximal end, theimplantation tool has a cross section which is substantially the same asthe outer cross section of the drill guide 22, of the cutter guide 24and of the control tool 26. The implantation tool 27 may comprise adepth stop 41 like the drill 23 and the cutter 25, which depth stop 41cooperates e.g. with the proximal face of the fixation/guide tool 21 orwith a corresponding stop shoulder inside the axial tunnel 32 of thefixation/guide tool. For giving the surgeon more freedom regardingimplantation depth it may be advantageous to not equip the implantationtool 27 with a depth stop but rather with one or a plurality of depthmarks (not shown) which show the surgeon how deep the implant isintroduced in the opening at any moment during implantation.

It is also possible to design the combination of implantation tool 27,implant 16 and fixation/guide tool 21 or part thereof as a load framecontaining a biased spring which is released for the implantation stepto provide the axial force and stroke necessary for the implantationstep. Suitable such load frames are disclosed in publication WO2009/109057, the disclosure of which is enclosed herein by reference.

Implantation of the implant according to FIG. 1 in a preferablyminimally invasive or mini-open procedure with the aid of the tool setaccording to FIGS. 5A to 5H comprises the following steps, which areschematically illustrated in the flow diagram of FIG. 6. The steps aredescribed hereinbelow.

Finding and marking the cut or fracture between the two bone portions bypositioning the protrusions 30 of the cut finder 20 in the cut orfracture, wherein the cut finder 20 is possibly introduced along apreviously positioned K-wire.

Positioning and fixing the fixation/guide tool 21 on the bone surfaceeach distal half portion on one of the bone portions by introducing thecut finder 20 into the axial tunnel 32 of the fixation/guide tool 21, bypushing the fixation/guide tool 21 against the bone until it abuts thebone surface, and by punching the spikes 33 or blades of thefixation/guide tool 21 into the bone surface using the punch 34.

Removing the cut finder 20.

Forcing the distal half portions of the fixation guide tool 21 againsteach other and locking them in the forced position.

Positioning the drill guide 22 in the axial tunnel 32 of thefixation/guide tool 21, making sure that its distal face abuts on thebone surface.

Positioning the drill 23 in one of the axial bores 35 of the drill guide22, drilling the first bore and repeating positioning and drilling forthe second bore, wherein the predefined depth of the bores is reachedwhen the depth stop 37 of the drill 23 abuts on the stop shoulder 36 ofthe drill guide 22.

Removing the drill 23 and the drill guide 22 from the fixation/guidetool 21.

Positioning the cutter guide 24 into the axial tunnel 32 of thefixation/guide tool 21 making sure that its distal face abuts on thebone surface.

For cutting a groove between the bores, positioning the cutter 25 intothe axial tunnel 38 of the cutter guide 24 and activating it and, ifapplicable, moving it laterally in the axial tunnel 38 of the cutterguide 24, wherein the predefined depth of the groove is reached when thedepth stop 40 of the cutter 25 abuts on the stop shoulder 39 of thecutter guide.

Removing the cutter 25 and the cutter guide 24 from the fixation/guidetool 21.

Controlling the accuracy of bores and groove by introducing the controltool 26 into the axial tunnel of the fixation/guide tool 21 and checkingthe introduction depth and removing the control tool.

If the controlled introduction depth is not o.k., repeating the steps ofintroducing the drill guide 22, of introducing the drill 23 and ofdrilling, the steps of introducing the cutter guide 24, of introducingthe cutter 25 and of cutting the groove, and the steps of introducingthe control tool 26 and of checking the introduction depth.

If the controlled introduction depth is o.k., introducing theimplantation tool 27 with the implant 16 mounted to its distal end intothe axial tunnel 32 of the fixation/guide tool 21 and transmittingenergy through the implantation tool 27 and into the implant 16 whileintroducing the implant into the bores and groove, wherein apredetermined depth of introduction is reached when the depth stop 41 ofthe implantation tool 27 abuts on the proximal face of thefixation/guide tool 21 or a freely selectable introduction depth isreached when a corresponding mark on the implantation tool has reachedthe proximal face of the fixation/guide tool 21. Separating theimplantation tool 27 from the anchored implant 16 and removing it fromthe fixation/guide tool 21.

Removing the fixation/guide tool 21.

The step of finding the cut or fracture using the cut finder and thestep of controlling the bores and groove using the control tool are notobligatory steps.

In a preferred tool set, the tools have the following further features,which may cooperate with further tools: For x-ray control of the correctposition of its distal protrusions in the cut or fracture, the cutfinder 20 (except for its distal protrusions) should have a sufficienttransparency for x-rays through its length and at the same time needs asufficient mechanical stiffness. Therefore it is proposed to e.g.manufacture the cut finder 20 of PEEK and to increase its transparencyby providing a plurality of through openings along its length, or tomanufacture it as a sandwich construction with two relatively thin rigidsurface layers (e.g. made from carbon or glass fiber reinforcedlaminates) oriented parallel to the longer extension of the crosssection and a center layer of foamed material (e.g. polyurethane foam)for better transparency. The fixation/guide tool 21 is designed to havea first axial length and in the region of its proximal end it comprisesmeans for removeably fixing a laterally extending handle piece. The cutfinder 20 has an axial length which is greater than the first axiallength and it comprises a through opening situated beyond the proximalface of the fixation/guide tool 21 when the cut finder 20 is positionedin the fixation/guide tool. For removing the cut finder 20 from thefixation/guide tool 21, the distal end of an angled remover tool (notillustrated) is introduced into the through opening and is pivotedupwards while the remover tool is supported on the proximal face of thefixation/guide tool 21. The punch 34 has an axial channel of the samecross section as the axial channel of the fixation/guide tool 22 and anaxial length such that the fixation/guide tool 21 and the punch 34together have and axial length which is larger than the axial length ofthe cut finder 20 such that the punch 34 can be positioned over theproximal end of the cut finder being positioned in the fixation/guidetool 21. The drill guide 22 and the cutter guide 24 have proximalflanges which rest on the proximal face of the fixation/guide tool 21when the distal end is positioned against the bone surface.

FIG. 7 is an axial section through an exemplary embodiment of thefixation/guide tool 21. In this figure the resiliently outward flaringdistal half portions 21.1 and 21.2 are visible as well as a forcingsleeve 30 with an inner cross section being slightly larger than theouter cross section of the fixation/guide tool 21 at its proximal endbut smaller than the distal face of the fixation/guide tool 21 when thehalf portions are in their outward flaring, i.e. non-forced position.The distal half portions 21.1 and 21.2 are forced against each other bymoving the forcing sleeve 30 in a distal direction, forcing the outwardsflaring half sections against each other. The movement of the forcingsleeve 30 relative to the fixation/guide tool 21 and its final positionare locked by e.g. a ratchet system 31 comprising two meshing linearracks with asymmetrical teeth, one rack arranged on the outside of thefixation/guide tool 12, the other one on the inside of the forcingsleeve 30. Any other per se known measure allowing movement of theforcing sleeve relative to the fixation/guide tool 21 in one directiononly or at least being able to lock the forcing sleeve 30 in a finalposition are applicable also. If the forcing sleeve 30 protrudes beyondthe proximal face of the fixation/guide tool 21, the forcing sleeve canbe moved distally using a suitable punch (not shown).

FIGS. 8A to 8C show a further exemplary embodiment of the implantaccording to the invention, whose form is quite similar to the form ofthe implant according to FIG. 1. FIG. 8A shows the implant in sectionperpendicular to its thickness T (parallel to the implantation directionI; section line A-A in FIGS. 8B and 8C), FIG. 8B shows the implant insection perpendicular to its depth D (implantation direction Iperpendicular to the paper plane; section line B-B in FIGS. 8A and 8C),and FIG. 8C shows the implant in section perpendicular to is width W(parallel to the implantation direction I; section line C-C in FIGS. 8Aand 8B).

The implant comprises two anchoring pins 1 and a bridge portion 2situated between the two anchoring pins 1. The anchoring pins 1 havepreferably a larger depth D and a larger thickness T1 than the bridgeportion 2.

The bridge portion 2 is e.g. made of a non-liquefiable (in the sense ofthe anchoring technique) material, e.g. of a metal (e.g. titanium ortitanium alloy), of a ceramic material (e.g. zirconium oxide) or of athermoset polymer or thermoplastic polymer (e.g. PEEK) having a meltingtemperature, which is sufficiently higher than the melting temperatureof the thermoplastic material comprised by the anchoring pins 1 which isto be liquefied. The bridge portion may also be made of a compositematerial comprising e.g. a trabecular metal (e.g. titanium or tantalum)and a thermoset or thermoplastic polymer. A composite materialcomprising endless fibers (e.g. carbon fibers) molded into a plasticmaterial (e.g. PEEK OPTIMA Polymer™) with the aid of the composite flowmolding process by the Swiss firm “icotec” is a further suitablematerial for the bridge portion. Non-resorbable polymeric or compositematerials used for the bridge portion are preferably equipped withosseointegration supporting means like e.g. a coating of hydroxyapatite.

The anchoring pins 1 comprise the thermoplastic material to be liquefiedat least on their surfaces to come into contact with the bone tissue orare e.g. made of this material, wherein, if the anchorage is to beachieved with the aid of mechanical vibration, the named surfacespreferably comprise energy directors (not shown) e.g. in the form ofprotruding humps or axial ridges. The anchoring pins 1 are joined to thebridge portion 2 by adhesion or, as illustrated on the left hand side ofthe implant of FIG. 8A, via a rough surface or surface structuresuitable for forming together with the liquefiable material a positivefit connection. For a stronger connection between the anchoring pins 1and the bridge portion 2 the latter may reach into or through theanchoring pins 1 as illustrated on the right hand side of the implant ofFIG. 8A. The implant is manufactured by e.g. positioning the bridgeportion 2 into a corresponding mold and injection-molding the anchoringpins 1 to or around the bridge portion 2.

The implant embodiment as illustrated in FIGS. 8A to 8C may furthercomprise an edge portion (not shown) connecting the two proximal ends ofthe anchoring pins 1 and covering the proximal face and possibly up toabout 20% of the depth of the bridge portion 12 and consisting of theliquefiable material. Such an edge portion of an implanted implantconstitutes a polymer seam tightly closing the cut or fracture. In afurther embodiment of the implant similar to the one shown in FIGS. 8Ato 8C the bridge portion as well as the anchoring pins are made entirelyof the liquefiable material (see also FIG. 1).

The proximal face 3 of the implant is preferably adapted to the bonesurface by e.g. being curved. As discussed already in connection withFIG. 1, the proximal face 3 preferably comprises means for the implantto be held by the implantation tool. Such means are e.g. axial openingsor bores 4 arranged e.g. in the region of the anchoring pins 1 andcooperating with corresponding protrusions provided on a distal toolface (see also FIG. 5H).

For an exemplary embodiment of the implant, the two thicknesses T1(anchoring pin) and T2 (bridge portion) are e.g. in the range of 1 to 3mm and 3 to 8 mm, the overall depth D is in the range of 5 to 20 mm,preferably 7 to 20 mm, the overall width Win the range of 5 to 20 mm,preferably 5 to 15 mm.

FIG. 9 is an axial section on a larger scale than FIG. 5H of the distalend of the implantation tool 27 and an implant similar to the oneillustrated in FIGS. 8A to 8C being mounted thereon for implantation.The implant is held on the distal tool end by protrusions 51 extendingfrom the distal tool face and being adapted to enter the openings 4 inthe proximal face 3 of the implant. As already mentioned further above,for optimal transfer of vibrational energy to the implant and therewithoptimal anchorage of the implant in the bone tissue it is preferablethat the form of the distal tool face matches the form of the proximalface 3 of the implant as exactly as possible, such enabling transfer ofthe vibration from the tool 26 to the implant over the whole distal toolface.

The implant according to FIGS. 1, 8A to 8C and 9, the implantationmethod according to FIGS. 3, 4 and 6 and the tool set according to FIGS.5A to 5H can be modified in e.g. the following manner, without departingfrom the basic idea of the invention.

The bridge portion 2 of the implant is bent or bendable to be notstraight and non-parallel to the device width W, the implant therewithbeing adapted or adaptable to better fit curved cuts or fractures(necessitates corresponding adaptation of the drill guide 22, the cutterguide 24, the control tool 26 and the implantation tool 27, and possiblyof the cut finder 20 such that the protrusions 30 define a curved lineinstead of a straight line).

Both the anchoring pins 1 and the bridge portion 2 of the implant aresubstantially made of a liquefiable material (see FIG. 1), wherein theimplant portions may be made of the same liquefiable material ordifferent such materials, and wherein the bridge portion 2 may carry acoating of a material which is capable of enhancing osseointegration.Such coating may e.g. comprise calciumphosphate or apatite.

Both the anchoring pins 1 and the bridge portion 2 are madesubstantially of a non-liquefiable material, e.g. of titanium or atitanium alloy or of a ceramic material. The non-liquefiable material ispreferably treated to have a surface structure, which in the region ofthe bridge portion 2 enhances osseointegration and which in the regionof the anchoring pins 1 is suitable for adherence of an at least partialcoating comprising the liquefiable material. Anchoring pins comprising ametal core have the advantage of being visible with X-ray and therewithfacilitating implantation. Such cores may also be removable afterimplantation.

The anchoring pins 1 have non-round cross sections (may necessitateadaptation of the drill guide 22 and possibly of the drill 23, which maybe replaced by e.g. a vibration driven punching tool as disclosed in thepublication US 2008/269649).

The proximal implant face is not adapted to a curved bone surface but ise.g. straight and extending e.g. perpendicular to the implantationdirection (necessitates corresponding adaptation of the distal face ofthe implantation tool 27).

The proximal face of the anchoring pins 1 does not comprise openings 4adapted to corresponding protrusions 51 of the implantation tool 27 butvice versa, or this proximal face is even. Further means and ways forattaching the implant to the distal end of the implantation tool aredisclosed in the above named publications U.S. Pat. No. 7,335,205 andU.S. Pat. No. 7,008,226.

The distal regions of the anchoring pins 1 and/or of the bridge portion2 are not tapering or the anchoring pins 1 and/or the bridge portion 2taper continuously or in steps over their whole depth, i.e. from theproximal face to their distal end (necessitates corresponding adaptationof the drill 23 and possibly of the drill guide 22).

The difference in thickness between the anchoring pins 1 and the bridgeportion 2 is small (<1 mm) and/or the anchoring pins are equipped withself-reaming structures, such enabling implantation without thenecessity of providing bores (use of the drill guide 22 and the drill 23may be eliminated, adaptation of the cutter guide 24 may be necessary).

No groove between the two bores is provided for the bridge portion 2(use of the cutter guide 24 and the cutter 25 may be eliminated).

The implant is a three-part (or multi-part) implant comprising two (ormore than two) anchoring pins and one bridge portion constituting three(or more than three) separate implant parts, wherein the bridge portionis first positioned in the cut or fracture and the anchoring pins arethen pushed through or past the bridge portion to be anchored in thebone tissue and possibly in the bridge portion (see also FIGS. 13 and14; necessitating a second implantation tool being equipped for energytransmission or not, depending on whether the bridge portion comprises aliquefiable material and is to be anchored in the tissue, or whether thebridge portion is made of a non-liquefiable material and is impactedinto the groove provided for it or into the cut or fracture).

The implant is a three-part implant comprising two anchoring pins andone bridge portion constituting three separate device parts, wherein theanchoring pins are first implanted (preferably simultaneously) and thebridge portion is then fixed to the two proximal faces of the implantedanchoring pins (necessitating a second implantation tool being equippedfor energy transmission or not, depending on whether the bridge portioncomprises a liquefiable material and is fixed to the anchoring pins bye.g. ultrasonic welding, or whether the bridge portion is made of anon-liquefiable material and is impacted into the proximal faces of theimplanted anchoring pins).

The implant comprises two separate anchoring pins and no bridge portion,wherein the two anchoring pins are preferably implanted simultaneously(use of cutter guide 24 and cutter 25 can be eliminated).

The implant comprises one anchoring pin and no bridge portion (drillguide 22 and implantation tool 27 may possibly be adapted, use of cutterguide 24 and cutter 25 can be eliminated).

The one- or three-part implant is anchored in the bone tissue usingelectromagnetic radiation (preferably in the visible or infraredfrequency range) for liquefaction of the liquefiable material. For thispurpose, instead of the implantation tool 27 being a vibration tool, theimplantation tool having the same form as the vibration tool but furthercomprises light guides with proximal ends being connected to a radiationsource (e.g. laser) and distal ends arranged at the distal tool face ina manner suitable for coupling the laser light into the anchoring pinsof the implant. Furthermore, the anchoring pins are designed to comprisein a central region a material which is transparent for the laser lightand capable of scattering it and near the surfaces where liquefaction isto occur a material capable of absorbing the laser light for creatingthe thermal energy needed for the liquefaction and anchoring. Theanchoring pins consist e.g. of one thermoplastic material which in apure state is transparent for the laser light and which in the centralregion contains a scattering agent and in a peripheral region anabsorbing agent, the agents being e.g. particulate or molecular. In FIG.9, the left hand side of the tool is shown comprising a light guide 45(dash-dot lines) and the left hand anchoring pin comprising a centralregion 46 with a scattering agent (indicated by short lines of varyingorientation) and a surface region 47 with an absorbing agent (indicatedby small circles). The two agents need to be adapted in a per se knownmanner to the electromagnetic radiation to be coupled into the anchoringpin. The radiation source is activated shortly before, during or afterthe implant is positioned in the opening. During liquefaction, apressing force is applied to the implantation tool for making theliquefied material to penetrate into the bone tissue.

FIG. 10 shows a further exemplary embodiment of the implant according tothe invention. The implant has approximately the same form as theimplant shown in FIG. 1 or 8A to 8C, but the anchoring pins 1 do notconsist fully of the liquefiable material or comprise this material ontheir surfaces but they comprise a perforated sheath 52 each and theliquefiable material is provided inside these sheaths 52, e.g. in theform of a polymer pin.

The method for implanting the implant as shown in FIG. 10 is differentfrom the method for implanting the implant as shown in FIGS. 1 and 8A to8C in that the implant needs to be positioned in the opening providedfor it and only then the liquefiable material is liquefied by beingpressed into the sheath 52 and simultaneously energy being transmittedinto it. On liquefaction the material is pressed through the perforatedwalls of the sheaths 52 to penetrate into the bone tissue in the liquidstate. For such liquefaction and pressing out, the implantation tool 27equipped for transmitting energy is applied to the liquefiable materialonly, which implantation tool 27 may comprise a forked distal endequipped for holding and guiding the implant on being introduced intothe opening and for transmitting energy to the liquefiable material ofboth anchoring pins 1 simultaneously. It is also possible to employseparate implantation tools for positioning the implant and fortransmitting energy to the liquefiable material and pressing it into thesheathes, wherein the implantation tool for the latter purpose may haveone only distal end (as illustrated) and the two anchoring pins areanchored in the bone tissue one after the other.

It is also possible to use vibrational energy not only for liquefyingthe liquefiable material contained in the sheaths 52 but also forfacilitating the positioning of the implant according to FIG. 10 in theopening provided for it, which is achieved by using an additionalvibration tool (not shown) suitable for transmitting the vibration tothe sheaths of the anchoring pins and/or to the bridge portion(vibration tool 27 e.g. as shown in FIG. 9).

It is also possible to first position the implant in the openingprovided for it without the liquefiable material being present in thesheaths 52 using a corresponding implantation tool and only thenintroducing the liquefiable material constituted by two polymer pinsadapted to the inner cross section and length of the sheaths 52 andtransmitting the energy thereto using a further implantation tool.

The embodiment as shown in FIG. 10 allows also using a bone cementinstead of the liquefiable material, or a polymer of a high viscosity,wherein the cement or polymer is made to harden or cure when pressed outof the sheath and into the bone tissue.

Instead of e.g. vibrating the liquefiable material positioned in thesheaths 52 it is possible also to couple a pin comprising theliquefiable material to a rotation drive, to introduce a distal portionof the pin into the sheath 52 and to liquefy the material by rotatingthe pin within the sheath 52 and at the same time pressing it into thesheath and holding the sheath for preventing it from rotating with therotating pin, such creating friction at least at the distal pin end andtherewith thermal energy which liquefies the pin material.

Furthermore, as already mentioned in connection with the implantaccording to FIGS. 8A to 8C and 9, it is possible also to couple,instead of vibrational or rotational energy, electromagnetic radiation(preferably of the visible or infrared frequency range) into theliquefiable material which is e.g. equipped for scattering the radiationand transmitting it into the sheath (e.g. made of metal) where it isabsorbed to create thermal energy which is able to liquefy thethermoplastic material at least partly. Absorption may also take placewithin the pin which for this purpose contains an absorbing agent. It ispossible also to design the sheath such that at least an inner surfacethereof can be heated electrically.

FIG. 11 shows a further exemplary embodiment of the implant according tothe invention and the distal end of an implantation tool 27 suitable forimplantation of the implant. The anchoring pins 1 of the implant areanchored in the bone tissue using the anchoring technique as describedin the publication WO 2009/055952. The anchoring pins 1 have the form ofpolymer tubes 57 and distal ends of the implantation tool 27 protrudethrough the tubes 57 and, adjacent to the distal ends of the tubes,carry distal foot pieces 58 which consist of the same polymer materialas the tubes 57 or of a different polymer material being weldable to thepolymer material of the tubes. This is shown on the left hand side ofFIG. 11.

The foot pieces 58 are fixed to the implantation tool 27 via aconnection (e.g. threads) which is able to transmit the energy from thetool 27 to the foot piece 58 and which is capable of being destroyedwhen the foot piece 58 is sufficiently warmed by the energy.

For the implantation, the implant as shown in FIG. 11 is held and guidedinto the opening provided for its implantation with the aid of theimplantation tool 27 and is held in place by a counter element 59. Theimplantation tool 27 is then e.g. vibrated and simultaneously pulled ina direction away from the implant. Through the vibrational energy, theliquefiable material of the distal end of the tubes 57 and possibly ofthe proximal face of the foot pieces 58 is liquefied and penetrates intothe bone tissue. Therewith the tubes 57 get shorter and are eventuallywelded to the foot pieces 58. As soon as a sufficient amount of theliquefiable material is liquefied and the foot pieces 58 are warmenough, the pulling force on the vibration tool 27 is increased forseparating the distal tool ends from the foot pieces 58, which remainanchored in the bone tissue to constitute distal ends of the anchoringpins 1 as shown on the right hand side of FIG. 11.

A similar implantation result can be achieved by using, instead ofvibrational energy, electromagnetic radiation which is coupled e.g.through the counter element 59 into the polymer tube 57 or through animplantation tool of the same form as the illustrated tool 27 into thefoot piece 58 to be absorbed in a distal part of the polymer tube 57 orin the foot pieces 58 of the tool, in the same manner as described forthe implant as illustrated in FIGS. 8A to 8C and 9.

FIG. 12 shows an anchoring pin 1 of a further exemplary embodiment ofthe implant according to the invention as well as a distal end portionof an implantation (preferably vibration) tool 27 suitable forimplantation of the implant. The implant may have a similar form as theimplant according to FIGS. 8A to 9C. The anchoring pin 1 of the implantis designed for being anchored in the bone tissue using the anchoringtechnique as described in the publication WO 2009/132472, the content ofwhich is enclosed herein by reference. This anchoring technique is acombination of the anchoring techniques as shortly described inconnection with FIGS. 10 and 11. For this reason, the anchoring pin 1comprises a perforated sheath 52 and the liquefiable material isprovided inside the sheath 52 in the form of a polymer tube 57 throughwhich the distal end of the implantation tool 27 reaches, carrying adistal foot piece 58 beyond the polymer tube 57. The polymer tube 57 isheld in place inside the sheath 52 with a counter element 59. Foranchoring it in bone tissue, the anchoring pin 1 as shown in FIG. 12 ispositioned in a corresponding bore, the polymer tube being held in placewith a counter element 59. Then, the implantation tool 27 is e.g.vibrated and is pulled in a direction away from the bone tissue, suchthat the polymer material is liquefied between the distal face of thepolymer tube 57 and the proximal face of the foot piece 58 and ispressed through the sheath perforations to penetrate into the bonetissue outside the sheath 52. Therein it is possible to equip the sheathwith perforations at a plurality of distinct depths and to liquefypolymer material in these distinct depth in distinct liquefaction stepsbetween which the foot piece is moved from one such depth to a nexthigher one, the vibration being switched off. After a last liquefactionstep the counter element 58 and the implantation tool 27 are removedfrom the sheath 52, wherein a rest of the polymer tube 57 and the footpiece 58 remain in the sheath 52 (similar to the anchoring process asdescribed in connection with FIG. 11) or are removed from the sheath. Inthe latter case the foot piece 58 may, as illustrated, be made of anon-liquefiable material.

In the same manner as described further above for the implants asillustrated in FIGS. 8A to 8C, and 9 to 11, implantation of the implantcomprising anchoring pins as illustrated in FIG. 12 is possible alsowith the aid of radiation energy (preferably laser light of the visibleor infrared frequency range) or rotational energy instead of the abovedescribed vibrational energy. For the latter case, an implantation toolof the same form as the above described vibration tool 27 is used and isconnected to a rotation drive, while the counter element 59 is equippedfor not only holding the polymer tube 57 against the foot piece 58 butalso for preventing the polymer tube from rotating together with thetool. Friction heat created between the distal face of the non-rotatingpolymer tube 57 and the proximal face of the rotating foot piece 58liquefies the distal end of the polymer tube and makes the liquefiedmaterial pass through the perforations of the sheath 52. Furthermore,liquefaction can be achieved by coupling electromagnetic radiation e.g.into the counter element 59 and from there into the polymer tube 57 tobe absorbed in the polymer tube 57 or in the foot piece 58. A furtherway for creating the thermal energy needed for the liquefaction consistsin electrically heating the proximal face of the foot piece 58.

FIG. 13 shows a further embodiment of the implant according to theinvention which implant, when implanted, resembles the implant accordingto FIG. 8A to 8C or 9 but before implantation comprises the anchoringpins 1 and the bridge portion 2 as separate parts (three-part implant orpossibly multi-part implant). The bridge portion 2 is designed for beingintroduced into the opening provided for it and for being then fixed byintroducing the anchoring pins 1 (preferably simple polymer pins)through bores 55 in the bridge portion 2 and anchoring them then in thebone tissue underneath the bridge portion. The bridge portion 2 ispreferably substantially wedge shaped and comprises two (or more thantwo) through bores 55 extending from the proximal face 4 to a distalface and preferably having a diameter which is smaller than thethickness of the bridge portion 2 at the proximal face 4 and larger thanthe thickness of the bridge portion 2 at the distal face such that thedistal bore mouths extend from the distal face onto the lateral surfacesof the bridge portion 2 towards the proximal face.

FIG. 13 shows on the left hand side the anchoring pins 1 before beingintroduced in the bores 55 of the bridge portion 2, i.e. it shows theimplant before implantation, and on the right hand side a sectionthrough the implant after implantation. For the anchoring pins 1 beingable to fix the bridge portion 2 firmly in the opening, it isadvantageous to provide in the bores 55 of the bridge portion 2 afurther liquefiable material which is welded to the liquefiable materialof the anchoring pins on implantation, or a surface structure, intowhich the liquefiable material of the anchoring pins is pressed onimplantation. A similar effect can be achieved by equipping theanchoring pins 1 with heads, or, as illustrated, to form such heads 56by applying further e.g. vibrational energy for plasticizing andcorrespondingly deforming the material of the proximal end of theanchoring pins 1.

For providing the bores in the bone tissue for accommodating the distalends of the anchoring pins it is possible to use a drill guide as shownin FIG. 5C or to use the positioned bridge portion 2 of the implant asdrill guide.

As already described for the implant as illustrated in FIGS. 8A to 8Cand 9, it is possible for the implant according to FIG. 13 to use forthe implantation or the liquefaction of the liquefiable materialrespectively, instead of vibrational energy, electromagnetic radiationand to provide means for absorbing such radiation in or adjacent to thelocation in which such liquefaction is desired. For such purpose, thebridge portion 1 comprises an absorbing agent or the radiation isabsorbed by the bridge portion 2.

Instead of the anchoring pins as illustrated in FIG. 13 to be anchoredin bores and possibly welded into the bridge portion with the aid of aliquefiable material and e.g. vibrational energy, it is possible also touse anchoring pins as illustrated in FIGS. 10 to 12.

FIG. 14 illustrates an exemplary application of an implant similar tothe implant according to FIG. 13. The bridge portion 2 of this implanthas the form of a part circle and is suitable for stabilizing a partcircular cut 13 e.g. produced in the tibial plateau leveling osteotomyillustrated in FIG. 2. The procedure of implanting the implant into thecircular cut may be the same as described before for the implantaccording to FIG. 13. Following an alternative procedure, the anchoringpins 2 are anchored in corresponding bores first and then the bridgeportion is positioned on the proximal heads of the anchoring pins andthe heads (not shown) of the anchoring pins are then formed. The boresfor accommodating the anchoring pins are drilled using a separate drillguide or the bridge portion.

In the implant according to FIG. 14 to be implanted as above describedit is advantageous to provide openings 55, which are not exactly adaptedto the cross section of the anchoring pins but are e.g. slot-shaped. Theproximal ends of the anchoring pins will adapt to the shape of theopenings during the head forming. Furthermore it may be advantageous notto provide a groove along the cut but to position the bridge portion onthe bone surface. For further stabilization of the bridge portion, thelatter may comprise a plurality of small thorns (not shown) along itslateral edges, which thorns are impacted in the bone surface onpositioning the bridge portion 2.

FIGS. 15A and 15B show a further embodiment of the three-part ormulti-part implant according to the invention, the embodiment beingbased on the same principle as the implant according to FIG. 13. Theimplant is illustrated in FIG. 15A viewed from the side of the proximalface and after implantation, and in FIG. 15B in section (section planedesignated with B-B in FIG. 15A) and in a partly implanted state. Theimplant comprises a bridge portion 2 and four anchoring pins 1, whereinthe bridge portion 2 has e.g. the form of a wedge and comprises twogrooves 60 on either side for receiving the anchoring pins 1.

In contrast to the implant illustrated in FIG. 13, the anchoring pins 1of the implant according to FIGS. 15A and 15B does not extend throughopenings in the bridge portion 2 but are positioned on both sides of thebridge portion, wherein a bore (or opening with another than circularcross section) adapted to receive one of the anchoring pins ispreferably situated partly in the bridge portion (groove 60) and partlyin the bone tissue.

As for the implant according to FIG. 13, the implant according to FIGS.15A and 15B are implanted by firstly pushing the bridge portion into theopening and by then positioning the anchoring pins and anchoring them inthe bone tissue. Therein the bores in the bone tissue for accommodationof the anchoring pins may be drilled before positioning the bridgeportion 2 using a drill guide e.g. as illustrated in FIG. 5C or they maybe drilled after positioning the bridge portion 2, using the latter as adrill guide.

Before implantation of the implant according to FIG. 13, a groove isprovided for the bridge portion 2, wherein a depth of the groove is thesame or larger than the depth of the bridge portion, such that onpositioning the bridge portion 2, its proximal face is flush with thebone surface. In a preferred application of the implant according toFIGS. 15A and 15B, the bridge portion 2 is made of a bone replacementmaterial such as e.g. calcium phosphate, hydroxyapatite, allograft bonetissue or a preparation made of allograft bone tissue, and the implantis used for stabilizing bone portions comprising bone tissue of areduced mechanical stability.

The anchoring pins 1 of the implant according to FIGS. 15A to 15B areagain anchored in the bone tissue with the aid of a liquefiablematerial, wherein the liquefiable material is arranged on the anchoringpins in any of the ways as discussed further above. Therein it isadvantageous to simultaneously with the anchoring in the bone tissue toconnect the anchoring pins with the bridge portion, e.g. by providing asuitably structured surface on the bridge portion where the anchoringpins are to be attached and by providing the liquefiable material onboth sides of the anchoring pins, on one side for establishing apositive fit connection with the bone tissue and on the other side forestablishing a positive fit connection with the surface structure of thebridge portion 2. Further examples of methods for in situ attachingimplant parts to each other and simultaneously anchoring them in bonetissue are described in the publication WO 2008/034276 which isincorporated herein in its entirety by reference.

FIGS. 16 to 19 show further exemplary embodiments of the implantaccording to the invention, the implants comprising numbers of anchoringpins and/or bridge portions which are different form such numbers of theembodiment according to FIGS. 8A to 8C. Virtually all above commentsregarding the implant, in particular the various designs of theanchoring pins as shown in FIGS. 9 to 12, the corresponding anchoringtechniques, and the design of multi-part devices as illustrated in FIGS.13 and 15A/B are adaptable to these further embodiments of the implantin a straightforward manner.

The implant according to FIG. 16 comprises one only anchoring pin 1 anda bridge portion 2 reaching laterally beyond the anchoring pin. Theimplant according to FIG. 17 comprises two anchoring pins 1 and atwo-part bridge portion 2 therebetween. The implant according to FIG. 18comprises two anchoring portions 1 and a bridge portion 2 reachinglaterally beyond the two anchoring pins 1 and comprising throughopenings. The implant according to FIG. 19 comprises two anchoring pins1 and a bridge portion 2 joined to the anchoring portion 1 in a centralregion between the distal and proximal ends thereof. All implantembodiments according to FIGS. 16 to 19 may comprise more than twoanchoring pins 1 and a corresponding number of bridge portions 2.

What is claimed is:
 1. An implant for stabilizing two bone portionsbeing separated by a cut or fracture in a human or animal patient, theimplant comprising a plurality of anchoring pins and at least one bridgeportion connecting proximal ends of the anchoring pins and wherein amaterial having thermoplastic properties is arranged on lateral surfacesof the anchoring pins or in a perforated sheath of the anchoring pins,wherein said surfaces of the anchoring pins or said perforated sheath isarranged on the implant for being in contact with bone tissue onimplantation.
 2. The implant according to claim 1, wherein the wholeimplant is made of the material having thermoplastic properties.
 3. Theimplant according to claim 1, wherein the material having thermoplasticproperties has a modulus of elasticity of at least 0.5 GPa and a meltingtemperature of at the most 350° C.
 4. A set of tools for stabilizing twobone portions separated by a cut or fracture in a human or animalpatient, the set of tools comprising an implantation tool and mounted ormountable to the implantation tool an implant according to claim
 1. 5.The set of tools according to claim 4 and further comprising afixation/guide tool comprising an axial tunnel and resilient outwardsflaring distal half portions with distal faces equipped for fixation ona bone surface.
 6. The set of tools according to claim 5 and furthercomprising means for forcing the distal half portions against each otherand locking them in a position resulting from the forcing.
 7. The set oftools according to claim 5 and further comprising at least one of a cutfinder, a drill guide and a corresponding drill, a cutter guide and acorresponding cutter, the cut finder, the drill guide and the cutterguide having cross sections adapted to the cross section of the axialtunnel of the fixation/guide tool.